The present invention relates to an apparatus applicable to image forming equipment for promoting easy positioning of an image carrier and a cartridge accommodating image forming process units which are to be disposed around the image carrier, as well as easy replacement of the cartridge.
An electrophotographic copier, facsimile machine or similar image forming equipment implemented by an electrophotographic procedure has an image carrier in the form of a photoconductive element, for example. A latent image electrostatically formed on the surface of the photoconductive element is developed by a developing unit, and the resulting visible image is transferred from the photoconductive element to a paper sheet. After such image transfer, the surface of the photoconductive element is cleaned by a cleaning unit. A current trend in the image forming art is toward a disposable cartridge in which various image forming process units including the developing unit are assembled integrally with and around the photoconductive element. At the present stage of technologies, although the service life of a photoconductive element is increasing, it is still shorter than the life of the body of image forming equipment with which the element is used. Therefore, it has been customary to install a photoconductive element in a cartridge together with image forming process units so that the cartridge may be bodily replaced to allow the equipment body to be continuously used.
A problem with image forming equipment of the type using a cartridge as stated above is that, when a certain process unit built in the cartridge reaches the end of its life, the cartridge has to be discarded together with the photoconductive element even if the latter is still usable by virtue of the ever increasing life. This increases the cost of the disposable cartridge and eventually forces the user to bear extra expenses.
In the light of this, there has been proposed an arrangement wherein the photoconductive element only is built in the equipment body while the process units to be disposed around the photoconductive element are assembled in a cartridge. This scheme allows only the cartridge, i.e., the process units to be discarded independently of the photoconductive element, but it is undesirable when it comes to positioning of the image carrier and the cartridge relative to each other. Specifically, the cartridge has to be replaced by opening a cover of the equipment body and then removing a face plate on which the cartridge is mounted from, for example, the front end of the equipment body. Besides, the construction is complicated because the face plate or similar member for mounting a cartridge is needed.
In general, two different approaches are available for the replacement of a cartridge in whichh process units are accommodated, independently of a photoconductive element. One approach is to arrange process units in a cartridge such that they will be situated around the upper half of a photoconductive element, and to allow the cartridge to be replaced in the up-down direction. This kind of scheme, however, has a drawback that the arrangement of the process units is severely restricted. The other approach is to configure a cartridge, in which process units are assembled, such that it is mounted and dismounted in the axial direction of a photoconductive element. This scheme brings about another drawback that, when a used cartridge is pulled out of an equipment body away from a photoconductive element, a cleaning and a developing unit become entirely open in the cartridge resulting in toner particles from being dropped or scattered around to smear the neighborhood. Moreover, when a fresh cartridge is inserted into an equipment body, it is apt to scratch or otherwise damage the photoconductive element. In any case, one has to replace the cartridge with greatest care. In addition, when one inadvertently touches the photoconductive element during replacement of the cartridge, the life of the photoconductive element is often reduced by grease.